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earthing main gas & water pipes

Discussion in 'Electrics UK' started by theflyingpig, 29 Jan 2007.

  1. theflyingpig

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    I'm in a block so no doubt these are earthed but I'm told I should have my own - what grade earth wire should i use?

    many thanks

    Huey
     
  2. DESL

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    It's all in the OSG
     
  3. JohnD

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    Main and Supplementary Bonding can be done by the householder, it is not notifiable work and does not have to be done by a qualified electrician.

    To the incoming metallic services which enter your property from outside (water, gas, oil, air con) you need 10mm G&Y taken to the Main Earthing Terminal which can be the service head by the company fuse, or can be inside the consumer unit, or can be an earth block near them. The wire must be continuous, not cut and joined. You can loop a single wire to more than one pipe if convenient. More often than not, homes have "protective multiple earth" and the electricity supplier provides an earthing point. If you do not have one, come back and ask again.

    In the bathroom, use 4mm G&Y to all the metallic pipes that enter the bathroom (this may include waste and soil pipes if lead or iron) and link these to the earth conductor of all electrical circuits that enter the bathroom. This will be lighting, may be a shaver socket, maybe electric shower, immersion heater, CH pump; extractor fan if not fed from the lighting circuit that is already bonded. You only need to link once to each circuit and one to each pipe at the point of entry (so if you have a light switch and eight lamps, you only need to bond to the lighting circuit earth once; and if you have a hot water pipe supplying basin, bath, shower and bidet, you only need to bond to the pipe once). If you have an adjacent airing cupboard that some or all the pipes pass through into the bathroom, you can bond there to avoid the visual impact of the wires. The bonding clamps must be accessible for inspection and maintenance, so not hidden under floors or behind tiles. Bathroom supplementary bonding does not have to go back to the meter, only to the circuits that enter the bathroom.
     
  4. theflyingpig

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    clear and consise answer - most helpful!

    the only circuit in my bathroom is lighting - two celing mountd bulbs and a pull switch - and there are no earths connected in any fitting. As they are overhead and untouchable does there still need to be earthing?

    and in the kitchen - I'm going to have to run the earth cable a rather long way around to get back to the CU - do i have to run a seperate earth wire for the gas pipe and the water pipe? Or can I run one wire to the kitchen, onto the gas pipe and then a short section from the water pipe to the gas pipe?

    thanks again!

    Huey
     
  5. JohnD

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    [​IMG]

    'mmmm sounds like you have an old 1960's lighting circuit with no earth. I think the answer should be yes but we need the advice of someone more familiar with the problem than me :oops: on what to do.

    It might not have to be in the kitchen. It is where the pipes enter your home. On the consumer's side of the stop-cock and/or meter, within 600mm.

    You can use a single piece with no joins. Run it in position and tack it to the walls, leave a lot of slack at the first pipe. You can remove a section of insulation without cutting the copper wire, twist this into a loop and trap it under the bolt washer at the first clamp, then continue the single, uncut, unjoined piece of wire to your second pipe. You will find this easier if you use good big pipe clamps - your supplier may have several qualities at different prices. The 10mm wire that you have to use is quite big.
     
  6. theflyingpig

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    thanks again JohnD - you are right re the age of the building - definitly 60's - I have to admit I'm not too bothered about the bathroom as there is no wiring anywhere other than the ceiling . . .

    10 mm is HUGE for the earth . . .its a local authority built flat block so my water main comes initially into an upstairs cupboard, but the gas main enters the property into the downstaris kitchen. I assume I need to leave the earths accessable?

    cheers
     
  7. JohnD

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    yes, the clamps must be accessible for inspection and maintenance, so not hidden behind tiles or anything. You will not want the expense of digging them out or fitting new ones when you come to sell the flat.

    The wire need not be on show.
     
  8. theflyingpig

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    OK - it'd be easiest for me to leave the clamps/connections exposed in the kitchen by the gas meter . .or does the water main earth HAVE to be at the pipes entry point to the flat?

    (last question I hope)!

    ta!

    oh - and where do I buy the 10 mm earth cable?
     
  9. davy_owen_88

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  10. theflyingpig

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    Well my stop cock is in the kitchen downstairs, and the main entry point in the cupboard upstairs . . . so i think I'll earth it in the kitchen alongside the gas meter. . .

    going to be needing about 20 metres to get back to the CU - any tipes as cheap place to buy it?

    cheers
     
  11. FootSore

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    JohnD excellent ansswer. Even I could follow that.

    Sort of. Just one quick clarification. Recently had two new bathrooms plumbed in and although they did the electrics the bathroom firm skipped the bonding in their quote! Thanks guys :rolleyes:

    I have purchased and fitted earth clamps and fitted to all pipes in the airing cupboard next to both bathrooms. This is also the spot for 95% of the electrics. All fans, lights & showers are connected via terminal blocks.

    Do I run earth cable from clamp to clamp in individual pieces or does it have to be continuous. Or do I run each clamp back to a metal earth block screwed to the wall. (Currently I have wired one to the next in separate pieces but this easily changed - and the total distance is < 1m for all connections)

    Connections:
    Gas In to Boiler
    Cold Water In
    Cold Water Out - Mains Pressure
    Cold Water Out - Balanced Pressure (3 Bar)
    Hot Water Out - Balanced Pressure (3 Bar)
    Towel Rads Flow
    Towel Rads Return
    Rads Flow
    Rads Return

    Then do I connect the 4mm earth to the wiring which is either 2.5mm or 1.5 mm depending & consequently doesn't have a 4mm earth.


    The only exception is an airspa bath that has its own supply cable & breaker at the CU. Do I just need to earth link this to a single pipe under the bath?

    All help appreciated.
     
  12. JohnD

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    You link them all together, including the CPC for the spa and the pipes to the spa. The reason for using 4mm even on a 2.5mm or 1.5mm supply CPC is that you might bump into the bonding cables or snag then with the hoover, so they are of a thicker size to compensate for lack of mechanical protection (this is easier and cheaper than trying to protect them which is an alternative permitted method with thinner wires).

    If you have metal earth blocks this is a very convenient way to gather together all the wires.

    If you are able to run a single unbroken wire between several clamps, this is I think slightly better than having lots of cut lengths, because it makes it less likely that if one is snagged and comes loose, all the others will be unprotected.
     
  13. FootSore

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    JohnD Thanks

    4mm is fine and I bought loads of it to cover the job - nearly 4 metres of the stuff at <£0.50/metre. I could afford to be extravagant! All the pipes are within <0.5m of each other.

    I will replace individual lengths with a continuous length as what you have said about hoovers or removal of a single link makes sense. (Even though they are nice and safe in the back of an airing cupboard). I do have an earth block but I think this will look messier than a single cable. and more terminations will canel out the extra effort of stripping insulation in the middle of a cable.

    The water pipes run from the airing cupboard to the airspa in copper with soldered joints so if I connect the CPC of the pump unit to the cold (and hot?) water pipe under the bath this will be OK as this is connected to everything else in the airing cupboard. Using the cold water pipe as part of the earthing circuit which I beleive is allowed.

    I understand the mechanics and the reasons for it just want to check that everything I do complies with best practice - and the regs.

    Thanks for the help.

    FootSore
     
  14. JohnD

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    If the spa supply does not have a convenient point to connect, except under the bath, then take it from there. Note that an electrical appliance under a bath must be protected with a fixed panel (you have to use a screwdriver or other tool to gain access)

    You are right, a metal pipe with permanent joints (e.g. soldered) can be used as part of the bonding circuit. If there are plastic parts or push-joints, run the cable back to another connection as well or bridge the earthwire over them.
     
  15. theflyingpig

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    Footsore - where did you buy your cable?

    cheers
     

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